New Dark Matter Model With Late-Time Drag Proposed to Explain Growth Rate Anomalies
Researchers have proposed a new dark matter model called interacting Decaying Cold Dark Matter (iDCDM) in which dark matter experiences increasing drag from dark radiation produced by dark matter decay at late times. The model was motivated by recent observations suggesting that large-scale structure growth at low redshift is slower than predicted by the standard Lambda-CDM model. The theory shows modest preference over standard models in current data and will be tested decisively by upcoming surveys like DESI, Euclid, and Rubin.
A new theoretical model of dark matter has been proposed to address potential discrepancies between observations of large-scale structure growth and predictions from the standard Lambda-CDM cosmological model. The model, called interacting Decaying Cold Dark Matter (iDCDM), introduces a mechanism where dark matter decays into dark radiation at late times, creating an increasing drag force on the dark matter—unlike conventional dark matter-dark radiation interactions that weaken over cosmic time. The model adds only two parameters beyond Lambda-CDM while preserving consistency with background expansion, Big Bang nucleosynthesis, and primary cosmic microwave background observations. When tested against current data, iDCDM shows a modest statistical preference over Lambda-CDM (with Δχ² ranging from -2.7 to -7.6), driven primarily by measurements of the growth rate parameter fσ8. The model makes distinctive predictions for a step-shaped suppression of the linear growth rate that can be tested with upcoming large-scale structure surveys.
What's missing
The study does not discuss potential observational signatures or constraints from other cosmological probes (e.g., supernovae, galaxy clusters, or other independent growth rate measurements) that might further test or constrain the iDCDM model. Additionally, the paper does not address how this model relates to other proposed solutions for the observed growth rate tension, such as modified gravity theories or other dark matter variants.
What different sources said
- arXiv astro-phCenter
Dark Matter with a Drag at Low Redshift
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